Added running task printline.
If the source folder doesn't exist for Java, fail the build immediately.
Implemented a Groovy plugin, it does the basics: such as compiling just Groovy(it could do Java if you threw it in the Groovy folder, but it isn't recommended just yet), jarring the file, and creating a manifest, just like the Java plugin. Also check if the build has failed, and if so totally return a BuildState.FAIL.